A fast growing market both in civilian and military business is geographical information systems. Knowledge about geographical conditions forms a fundamental decision support to companies, authorities and in the military. The geographical information can comprise digital maps having superposed information layers such as infrastructure, terrain type and different types of objects. This way of providing digital maps is time consuming and comprises forming two dimensional maps comprising capturing images of the terrain from an aircraft and post-processing of the captured images. It is an even more time consuming process to form three dimensional maps from captured images or range data sets of the terrain/infrastructure.
WO 2009/003529 relates to another type of geographical information system. It relates to an arrangement and a method for providing a three dimensional map representation or a model of an area. The arrangement comprises a processing unit arranged to, for a plurality of time recorded, overlapping images of the area to be stereo processed, associate navigation states so that each pixel of each time recorded image is correlated to a corresponding navigation state and to perform the stereo processing based on the associated navigation states so that all pixels in the map representation or 3D model are specified in three geographical dimensions.
One problem with the stereo processing of overlapping images is that a sharp spatial change tends to disappear or partly disappear during the stereo processing since only a part of the overlapping images catches the sharp spatial change. One way to overcome this problem is to introduce a laser rangefinder or a LIDAR device in the vicinity of the imaging device. Laser range measurements are conducted on a particular object or area during the period when the overlapping images are taken of the particular object or area. Each laser range measurement is very accurate at a single point and can be used to improve the accuracy of the 3D model.
US2010/0204974 discloses a LIDAR and one or more electro-optical (EO) imaging device which may asynchronously acquire LIDAR shots and EO images. Navigation and timing data may be used to associate a particular LIDAR shot and/or EO image with navigation data. The navigation data may be used to cross correlate a LIDAR shot to a selected plurality of overlapping EO images. Ranging model information may be determined from EO image sequences using a stereo imaging technique. The stereo imaging technique may be seeded using the LIDAR shot data.
One object of the present invention is to further improve modelling.